Linux 4.9 compat: inode_change_ok() renamed setattr_prepare()

In torvalds/linux@31051c8 the inode_change_ok() function was
renamed setattr_prepare() and updated to take a dentry ratheri
than an inode.  Update the code to call the setattr_prepare()
and add a wrapper function which call inode_change_ok() for
older kernels.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Requires-spl: refs/pull/581/head

config/kernel-setattr-prepare.m4

@@ -0,0 +1,23 @@
+dnl #
+dnl # 4.9 API change
+dnl # The inode_change_ok() function has been renamed setattr_prepare()
+dnl # and updated to take a dentry rather than an inode.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SETATTR_PREPARE],
+	[AC_MSG_CHECKING([whether setattr_prepare() is available])
+	ZFS_LINUX_TRY_COMPILE_SYMBOL([
+		#include <linux/fs.h>
+	], [
+		struct dentry *dentry = NULL;
+		struct iattr *attr = NULL;
+		int error;
+
+		error = setattr_prepare(dentry, attr);
+	], [setattr_prepare], [fs/attr.c], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_SETATTR_PREPARE, 1,
+		    [setattr_prepare() is available])
+	], [
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -74,6 +74,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_ENCODE_FH_WITH_INODE
 	ZFS_AC_KERNEL_COMMIT_METADATA
 	ZFS_AC_KERNEL_CLEAR_INODE
+	ZFS_AC_KERNEL_SETATTR_PREPARE
 	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
 	ZFS_AC_KERNEL_D_MAKE_ROOT
 	ZFS_AC_KERNEL_D_OBTAIN_ALIAS

include/linux/vfs_compat.h

@@ -444,4 +444,15 @@ static inline void zfs_gid_write(struct inode *ip, gid_t gid)
 #define	zpl_follow_up(path)			follow_up(path)
 #endif
 
+/*
+ * 4.9 API change
+ */
+#ifndef HAVE_SETATTR_PREPARE
+static inline int
+setattr_prepare(struct dentry *dentry, struct iattr *ia)
+{
+	return (inode_change_ok(dentry->d_inode, ia));
+}
+#endif
+
 #endif /* _ZFS_VFS_H */

module/zfs/zpl_inode.c

@@ -323,7 +323,7 @@ zpl_setattr(struct dentry *dentry, struct iattr *ia)
 	int error;
 	fstrans_cookie_t cookie;
 
-	error = inode_change_ok(ip, ia);
+	error = setattr_prepare(dentry, ia);
 	if (error)
 		return (error);